1. Field of the Invention
The present invention relates to a rivet gun and more particularly to a rivet gun having one or more buffer devices.
2. Description of Related Art
With reference to Taiwan patent application No. M400369, a rivet gun is used to rivet a rivet in two boards to fix the two boards together. A rivet usually has a head and a shaft connected to the head, and the shaft is usually longer than the head.
A rivet gun usually has a barrel, a handle, a trigger, an inflator and a piston assembly. The barrel has a rivet assembly mounted inside the barrel. The handle extends vertically and downwards from the barrel and has a gas channel formed in the handle. The trigger is mounted on the handle and connected to the gas channel. The inflator is mounted on a bottom of the handle and connected to the rivet assembly to actuate the rivet assembly by hydraulic pressure. In addition, the inflator can be connected to a high pressure gas source to inflate a high pressure gas into the barrel for ejecting a shaft of a rivet out of the barrel. The piston assembly is movably mounted in the inflator and has a piston rod and a piston head connected to the piston rod. A through hole is formed through the piston head through which an inserting tube is mounted. The inserting tube is connected to the bottom of the handle.
When the rivet gun is used to rivet a rivet, the rivet penetrates through two boards, and then the trigger is pulled. A head of the rivet abuts a front end of the barrel and is clamped by the rivet assembly. Meanwhile, the head of the rivet is pressed by the barrel and becomes T-shaped to fix the rivet on the boards. Simultaneously, the high pressure gas of the high pressure gas source is inflated into the barrel, a backward suction is formed and a section fractured from a shaft of the rivet is ejected out from a rear end of the barrel by the backward suction.
The piston head of the piston assembly of the rivet gun is disc-like and contacts an inner wall of the inflator in an air tight manner to divide an inner space of the inflator into an upper air chamber and a lower air chamber. However, the piston head is solid, thus, when the trigger is pulled for riveting, the high pressure gas inflates into the lower air chamber, such that the piston head moves upward. The piston head is suddenly pushed by the high pressure gas and shakes, and noise is produced by the piston head. On the contrary, when the riveting is finished, the piston head moves downward, but the lower air chamber still contains air, such that the piston head cannot move to a bottom of the inflator immediately.